I am trying to draw the best illustration I can for a user manual. I have a CAD drawing in .STP and I would like to get some simple illustations in .AI or .EPS or .SVG

I tried to export the illustrations with a couple of CAD programs (3D Via Composer, 3D MAX) and import them into Illustrator. The drawings are innacurate, borders aren't curved but made with several segments.

How should I handle this?

  • How are you exporting the drawings? I get 3D CAD drawings exported to .dxf format, which Illustrator handles very well.
    – MarkS
    Commented Sep 3, 2015 at 13:06
  • Dxf, dwg or svg - I decided to use 3D Via Composer because I am getting some improvements. I am trying to get something with fewer details and better shapes. Edit: with details I meant fewer lines. Every line exported has at least 3 more lines above.
    – Marie
    Commented Sep 3, 2015 at 14:03
  • I suppose that the only way is to manually delete the extra details.
    – Marie
    Commented Sep 3, 2015 at 14:11
  • @Marie Not really there exist a bazillion CAD tools that pre simplify your models.
    – joojaa
    Commented Sep 3, 2015 at 15:08

1 Answer 1


All current, generation of CAD and DCC software make the hidden line removal on discrete (tri or quadrangulate) data. There really is no good way to handle it otherwise available in the open market*.

Rhino can do a NURBS silhouette line fit, this is not exact either by any means as there is still a discretisation step but at least it refitted on the surface curvature. The biggest problem is that not all NURBS surfaces can be made into 3 degree beziers. Though this might not matter much to you.

What one usually does is called secondary fitting. Here you run a curve simplified after the rendering process (or at cut phase if you use a algorithm that more resembles painters algorithm). You can do this in illustrator although the fitter is not terribly interesting and does some fitting misses at edges. If you can use the Astute Graphics simplifying tools they much better, though i don't have it at home

One possible workflow is as follows:

  1. I usually pre-simplify the geometry in the CAD if I don't need the details. This is relatively easy and painless with newest line of CAD software. This is often MUCH faster as there is less primitives in 3D.

    3D simplification

    Image 1: A Kuka KR6 SIXX (SIXX nolonger exists. So the closest new one is KR-agilus series** ← Model available on registration) before (Left) and after simplification (Right).

    But while I was at it, I ended up simplifying for 2 minutes more after that capture.

  2. I convert that to a drawing and export as PDF.

    Because I'm doing secondary fitting i put the edge quality to sky high.

  3. Once i get the cad data out of the system (in this case CREO), i run a simplification of the data. If no better simplify routine exists i choose to run Object → Path → Simplify... With 100 fidelity 2-3 times.

    This may not work so well out of 3DS MAx as it connects too much data whereas Creo natively exports separated segments so be careful.

    Usually i also join curves at this point to kill some excess geometry. I'm now down to about 900 points form a 8000. With no more noticeable problems.

    Simplified 2d

    Image 2: After vector import (Right) and secondary fitting (Left).

  4. I quickly clean of any excess and make sure I'm using a round edged brush.

    Final piece

    Image 4: Final piece. Usually i take a bit more time than 15 minutes STEP to illustration, like in this case, but this is a demo after all.

* that is to say not available to buy, but they certainly do exist, but seems to me that it's no better than secondary fitting anyway.

** Which is virtually identical.

  • thanks for posting this process. I am missing how you are getting the vectors out of 3ds Max? Commented Jun 21, 2018 at 21:12
  • @maxehrlich there is a separate vector rendering engine that ships with MAX, or atleast it used to ship havent checked in a while.
    – joojaa
    Commented Jun 22, 2018 at 7:37

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.